Large wholesale processing machines which process photographically sensitized webs are well known. These machines can run at speeds of up to 50 meters per minute depending on the number of tanks through which the web must pass to be processed. Further, such machines can be sufficiently wide to accommodate up to 6 separate webs moving in parallel through the machine. Most of these machines are individually configured from standard components to suit individual laboratory requirements.
Recent developments have shown that the chemical volume of the prior art large volume tank processing machines described above can be reduced by up to 90% by including a volume filling rack within each tank. Such a low volume thin tank (LVTT) type apparatus is disclosed in U.S. Pat. Nos. 5,179,404; 5,311,235; 5,309,191; 5,339,131 and 5,387,499. A limit to the maximum practical volume reduction is the space needed for the reliable transport of the webs through the tanks and the efficient recirculation and/or replacement of the chemicals used in the tanks.
As a result of reducing the volumes of tanks in a processing apparatus, new chemical formulations (such as Redox Amplification (RX) formulations) can be used which shorten the time of the various processing steps occurring in the tanks, thereby leading to increases in the line speed of the processing apparatus.
Although the new chemical formulations mentioned above can result in faster development of a photographically sensitized web, efficient usage of the chemicals relies on the chemicals being rapidly brought into contact with the sensitized web and then being quickly removed and replaced by fresh chemicals when the chemicals become exhausted. This action is normally known as agitation. In small machines a chemical recirculation pump is used to provide the agitation by quickly turning the tank contents around at anything up to about 12 times per minute. In the large wholesale machines, however, which hold about 250 liters per tank in an LVTT-type apparatus, the pump size required to obtain sufficient agitation (i.e. chemical replacement) becomes excessive.
With the foregoing in mind, the present invention aims to provide an improved rack for use in a low volume thin tank processing apparatus which assists in overcoming the problem highlighted above.